Servo brake operating mechanism for vehicles



Feb. 18; 1947. 2,416,222

SERVO BRAKE OPERATING MECHANISM FOR VEHICLES Filed NOV. 13, 19.44

Attorneys Patented Feb. 18, 1947 I sEnvo BRAKE OPERATINGMECHANISM FORVEHICLES v 1 John Rodway, LincolmEngland Application November 13, 1944,Serial No. 563,267 1 In Great Britain uly 12, 1943 a 6 Claims. 1 Thisinvention relates to Servo brake operating mechanism for vehiclesand tothe kind which includes two independent control levers either of whichcan be operated to apply the same brake or brakes and each of which isprovided with an independent mechanical transmission mechanism to enablethe brakes to be applied mechanically by operation of either lever inthe event of the failure of the power supply.

The object of the present invention is to provide an improvedconstruction or arrangement applicable to a vehicle in which the brakesare ordinarily applied by means of a pedal controlled Servo device butin which a hand lever is also provided to control small movements atslow speed such as are required during the operations incidental to theparking of a vehicle. .The.in vention is particularly designed to enablesuch operations to be carried out with Servo assistance andwithout theexcessive torsional load'in the brake cross shaft which occurs in moreusual arrangements. I I

According to the present invention Servo brake operating mechanism fora, vehicle comprises two independent control levers either of which canbe operated to apply the same brake or brakes wherein actuation of oneof said control levers causes operation of a, main-Servo device and anauxiliary Servo device to assist the application of the brake or brakesand operation of the other control lever causes operation of theauxiliary Servo device only to assist the application of the brake orbrakes.

According to one form of the invention the improved Servo brakeoperating mechanism for a vehicle comprises two independent controllevers, either of which can be operated to apply the same brake orbrakes with the assistance of a main Servo device and an auxiliary Servodevice in the case of the one lever and with the assistance of theauxiliary Servo device only in the case of the other lever, the powerexerted in said Servo devices being transmitted to the brake cross shaftat two spaced points for the purpose of effecting a substantiallyreduced torsional loading upon the said cross shaft.

Reference will now be made to the accompanying drawings which illustrateconstructions according to the invention and in which:

Fig. 1 shows diagrammatically a vacuum actuated Servo device forcontrollingthe brakes of a vehicle and Fig. 2 is a detail H view showinga form of changeover valve suitable fora pressure actuated srst ma In.the construction illustrated in Fig. l the brakes of a vehicle areadapted to be applied either by means of a hand lever l or a foot pedal2, the hand lever being adapted to operate through transmission rods 3and 4 and the foot pedal through transmission rods 5 and 6 onto a crossshaft 1 which is in turn connected by rods 8 and 9 to the brakemechanism on the wheels. The foot pedal 2 is connected by the rod 5 withthe reaction lever mechanism ll] of a master Servo device ll whoseoperating cylinder I2. is connected through a distributor valve 13 andconduit 14 to a source of vacuum. The reaction lever arrangement I0 isconnected by the rod 6 to the cross shaft 1. The master Servo "deviceindicated generally at I l and its distributor valve l3 will not bedescribed in detail as they are of known type and a similar arrangementis fully described for example,.in the specification on United StatesPatent No. 2,358,753, granted September 19, 1944.

The cylinder l2 of the master Servo device is connected by a pipe I5with a casing l6 from which a connection. I! passes to the cylinder isof an auxiliary or slave Servo device 19 whose piston .20 is connectedthrough levers 2| and'rod 22 to the cross shaft 1. This auxiliary Servodevice has no distributor valve and is not directly connected to thesource of vacuum but obtains its power when required in either of twodifferent ways according to the conditions under which the vehicle isbeing operated. A changeover valve is mounted within the casing l6 andcomprises two valve members 23 and 24 mounted on a com monstem 25 andadapted to co-operate respectively with seatings 26 and 21 fixed withinthe housing l6. Whenever vacuum is exerted in the cylinder I2 of themaster Servodevice such vacuum is also exerted through pipe I 5 andcasing I6 to unseat the valve member 23 and to seat the valve member 24so that the vacuum is also exerted through connection I! and in theServo cylinder 18.

The power thus exerted simultaneously in both Servo devices istransmitted to the cross shaft 1 through the rods 6 and 22. In practicethe rods 4 and 6 would be placed nearer to the right hand sideof thevehicle and therod 22 nearer to the left hand side of the vehicle sothat the power is transmitted to the cross shaft 1 at two spaced pointsthereby conducing to, even distribution of power to the brakes on eitherside of the vehicle and appreciably reducing the torsional loadcarshaft; l...

I posed between their respective seatings.

The brake operating hand lever I is connected to the cross shaft 1through the medium of a known form of lost motion mechanism indicatedgenerally at 28 and including levers Hand 30 connected by a common pivotindicated at'3l, the lever 29 being connected to the rod 3 and thepiston rod 39 of a reaction valve cylinder 32. The lever 29 has-lostmotion connections with a fixed pivot 33 around which lever 30 ismovable and with a pivot 34 at the opposite end of the said lever 30.The reaction valve which is housed within the cylinder 32 is also ofknown type and comprises a piston 35 which, when moved by actuation ofthe hand lever, unseats a valve member 36 from a seating on the end of avacuum connection 31 so that, thereafter, the vacuum tends to oppose theeffort applied through the handlever l. The cylinder 32 is connected bya pipe 38 with one end of the casing is of the changeover valve so thatwhen the hand lever l is operated to apply the brakes the mechanicaltransmission 3--28-4 will tend'to put the brakes into operation whilstthe reaction valve in cylinder 32 will place the source of vacuum supplyin communication with the changeover valve in such a way as to move itto a position wherein valve member 23 is seated and valve member 24 isunseated. Communication with the cylinder l2 of the master Servo deviceis thereby shut-off and the cylinder ll! of the auxiliary Servo deviceis r placed in direct communication through pipes l1,

housing I6, pipe 38, cylinder 32 and pipe 31 with the source of vacuum.In this way the movement of the hand lever l is provided with Servoassist-' ance one, scale suitable to the speed of movement of thevehicle when under control by the hand brake lever 1, while the power isapplied to the auxiliary Servo deviceproportionally to theeffoi'texerted on the hand lever. In this case, also,the loads applied-to thebrake cross shaft are such as will materially reduce the torsional loadcarried by'theicentral portion of the cross shaft;

Although the invention has been particularly described above inconjunction with a'vacuum system it is equally applicable to an airpressure system subject to alteration in the positions of the valveseatings in the changeover valve it, which is shown separately in Figure2 as applicable'to the use of air pressure. In this arrangement themovable valve member's23 and 24 are dis- The connections to thecylinders l2, l8 and 32 would also need to be varied to enablethe airunder pressure to act upon the opposite sides of their respectivepistons; to thoseiused for'the vacuum system. V 1

I Iclaim: g e

1. Servo'brake mechanism for a vehicle, com- I prising a brake crossshaft, a control lever, a

Servo cylinder embodying reaction mechanism, connections between thereaction mechanism of said cylinder, said controllever and said crossshaft, a second control lever, a. reaction valve operative by saidsecond control lever, an auxiliary Servo cylinder, a connection betweensaid auxiliary Servo cylinder and said cross shaft, connections betweensaid reaction valve and both of said Servo cylinders, anda changeovervalve interposed in said last-mentioned connections and adapted torender operative the auxiliary Servo cylinder independently of thefirst-mentioned Servo cylinder when the second'control lever isactuated.

. 2.. Servo'brake mechanism accordin to claim l,

' wherein said reaction valve is operable by said I 4 second controllever to move said changeover valve to a position wherein said auxiliaryServo cylinder is placed in direct communication with a source of power,and including lost-motion mechanism connecting said second control leverto the brake applying means and to said reaction valve to thereby enablepower to be applied to the auxiliary Servo cylinder proportionally tothe efiort exerted and on a scale suitable to the speed and movement ofthe vehicle when under control of said second control lever.

3. Servo brake operating mechanism for a vehicle, comprising a masterServo cylinder having a piston therein, an auxiliary Servo cylinderhaving a piston therein, a brake cross shaft, means connecting thepistons in both of said cylinders to said cross shaft, two independentlyoperable control devices, means actuated by one of said control devicesto operate the master Servo cylinder, means connecting the auxiliarycylinder to a source of power when the master cylinder is operated, andmeans actuated by operation of the other of said control devices to shutoff the master cylinder from the auxiliary cylinder and to 0perate thecross shaft andbrakes from said auXiliary cylinder only.

4. Servo brake operating mechanism accordin to claim 3, wherein saidlast named means comprises a casing, a pair of valve members therein,

inder is in communication with the source of power or to place theauxiliary cylinder in direct communication with the source of power whenthe master cylinder is inoperative.

.5. Servo brake operating mechanism according to claim 3, wherein saidcontrol device for said master Servo cylinder is a foot pedal operableto cause said master Servo cylinder to be placed in communication withthe source of power and with said auxiliary Servo cylinder whereby poweris ex erted in both of said cylinders simultaneously for actuating saidbrake applying cross shaft.

6. Servo brake operating mechanism, comprising two independent controllevers either of which is operable to apply the same brake applyingmeans, a reaction valve interposed between one of said control leversand the brake applying means, a master Servo device having reactionmechanism connected to the other of said con,- trol levers and tothebrake applying means, an

auxiliary Servo device also connected to said brake. applying means,connections between said reaction valve and said master Servodevice anda REFERENCES CITED The following references arepof record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 11,848,458 Bragg et al Mar. 8,1932 1,650,488 Bragg et a1. Nov. 22, 1927- 2,042,392 Dewandre May 26,1936 JOHN RODWAY.-

